The present invention relates to a video imaging apparatus, and more particularly to an imaging apparatus characterized by varying an area from which a signal of an imaging element is read out.
Further, the present invention relates to a video camera using a solid state imaging element, and more particularly to a method of monitoring a current imaging condition when movement of a camera is prevented electronically.
Recently, an imaging apparatus is made small in size and light in weight and the magnification of a zoom lens tends to be increased. Thus, when a picture is taken by hand, the picture tends to be blurred by movement of the hands. As a prior art for suppressing the movement of the picture, there is known a method described in Japanese Patent Publication Nos. 1-53957 and 2-32831. In this prior art method, a movement of an imaging apparatus is detected by a rotating gyroscope. An optical system including from a lens to the imaging apparatus is moved on the basis of the detected result, or a transfer of a signal from an imaging apparatus is divided into a high speed transfer and a normal transfer to control the number of signals to be transferred in the high speed transfer. The latter is characterized in that an apparatus therefor can be made small in size.
However, the above prior art method does not considered that two pixels in the vertical direction of the imaging element are read out simultaneously. This simultaneous reading of two rows is an indispensable method necessary to eliminate a remaining image of a frame. When the number of signals to be transferred is increased or decreased while reading two pixels simultaneously, the transfer can be usually made only in a unit of two-pixel pitch even if an area of pixels to be transferred is minimum. Accordingly, a picture having a suppressed movement of an image is moved awkwardly.
In addition, recently, with the development of small and light household video cameras and high magnification of lenses, a video camera having less movement of an image without use of a tripod is highly desired.
As means for correcting the movement of the image, a method using an image memory is known, for example, as described on pages 377 to 378 in a collection of preprints for Lectures in a National Convention of the Institute of Television Engineers of Japan (1987). In this method, movement and vibration of a picture due to movement of a camera are detected as a parallel movement amount of the picture to calculate a correction amount on the basis of an amount and a direction of the parallel movement, that is, a vector so that the image is moved by the correction amount through the image memory to correct the movement and vibration of the picture.
As methods of correcting (preventing) the movement of the hands in the photography by a camera, there are the mechanical method using the gyroscope or the like as described in Japanese Patent Unexamined Publication No. 60-14330 described above and the electrical method of correcting the movement of the hands by using the image memory to devise the special processing of signals and the reading method of an imaging element. The latter has an image memory or an imaging element providing an image signal for a wider area than an area from which a TV signal is produced and selects a proper area in the whole area to produce the image signal in the selected area as the TV signal. Accordingly, even if movement of the hands occurs and the angle of field of the image memory or the imaging element is varied, the image signal in the same area as that before the occurrence of the movement of the hands is produced as the TV signal so that the TV signal having the same angle of field before and after the movement of the hands is obtained to thereby correct the movement of the hands.
In a camera which corrects movement of the hands electrically, for example, as shown in FIG. 1A, when an area of a light receiving plane 401 of an imaging element has an image room of 10% in the vertical and horizontal directions as compared with an area from which the TV signal is produced, movement of the hands up to 5% in the vertical and horizontal directions can be corrected as shown in FIG. 1B (in the case where the center of the TV signal before the movement of the hands is the same as the optical center of the imaging element).
As shown in FIG. 1C, when the TV signal area 402 is deviated or moved up due to the movement of the hands to come into contact with an upper edge of the light receiving plane 401, there is no room for correcting the upward movement of the hands and the upward movement of the hands can not be corrected.
As described above, even if the movement of the hands occurs as shown in FIGS. 1B and 1C, the image in the TV signal area 402 is not changed by the correction of the movement.
The area 402 is observed through a view finder as a monitoring picture. Accordingly, there is an disadvantage that it is impossible to determine whether the movement of a camera occurs or not as far as the area is observed through the view finder.